1. Field of the Invention
The present invention relates to substrate processing apparatus and, more particularly, to the mounting of a substrate transfer robot to a transport chamber.
2. Prior Art
U.S. Pat. No. 4,951,601 discloses a substrate processing apparatus with multiple processing chambers and a substrate transport apparatus. U.S. Pat. No. 5,270,600 discloses a coaxial drive shaft assembly of a substrate transport apparatus.
In many substrate processing applications a substrate transport apparatus includes a substrate transport robot which is mounted to a central, transport chamber. Typically, the transport robot has an arm assembly which operates in the transport chamber to transfer a substrate to and from adjacent chambers. Prior to operation, the transport robot is taught the locations of the adjacent chambers in which the substrate is to be transported for processing. It can be appreciated that teaching the precise location of each of the chambers prevents an undesired collision of the substrate with the walls of the chambers while the substrate is being transported. A collision may damage the substrate.
Teaching the location of each of the adjacent chambers is often performed at atmospheric pressure. During normal non-teaching operation, however, the transport chamber is usually evacuated to a desired operating vacuum pressure. Mechanical deflections may occur in the transport chamber as a result of this evacuation. The mechanical deflections may result in a significant variation in the location of the transport robot which is mounted to the transport chamber. As the location of the transport robot varies, the location of each of the processing chambers relative to those taught to the transfer robot prior to operation varies. Variations caused by mechanical deflection are particularly significant as the size of transport chambers increase to accommodate larger substrates.
Prior art solutions to the mechanical deflections and resulting variations in the locations of the transport robot and processing chambers included strengthening the transport chamber with structural supporting members, for example, steel support beams. While the structural supporting members may be effective in preventing the mechanical deflections, the additional weight and cost of the additional material typically violate design constraints. Also, the handling and the assembly of the chambers with the structural supporting members becomes more complicated.
It is an object of the present invention to provide a method for mounting and aligning the substrate transport robot to the transport chamber which minimizes the effects of chamber deflection and maintains the accuracy of the location of the mounted transport robot during operation.